/*
 * This code is from "Algorithms in C, Third Edition,"
 * by Robert Sedgewick, Addison Wesley Longman, 1998.
 */
#include <stdio.h>
#include <stdlib.h>
typedef struct node *link;
struct node
  { int v; link next; };
link NEW(int v, link next)
  { link x = malloc(sizeof *x);
    x->v = v; x->next = next;     
    return x;                         
  }
main()
  { int i, j; link adj[V];
    for (i = 0; i < V; i++) adj[i] = NULL;
    while (scanf("%d %d\n", &i, &j) == 2)
      {
        adj[j] = NEW(i, adj[j]);
        adj[i] = NEW(j, adj[i]);
      }
  }